The present invention relates to improvements in work feeders for sewing machines.
For many years, sewing machines have been provided with a feed mechanism, usually located in an opening in the work surface of the machine adjacent the stroke of the sewing machine needle and operating to engage the undersurface of the material being sewn and to advance the material to, and past, the needle. Because such a feeding arrangement only acts positively on the lowermost surface of the plural layers of material being sewn, it has long been desired to provide in a sewing machine an arrangement which would achieve a positive feed of the upper layer of material in addition to the conventional positive feed of the lower layer of material. While various approaches have been attempted (e.g., rotary feed wheels driven through flexible cables), success was minimal until the introduction of my "top feeder" that operated in synchronism with the conventional lower work feeder to provide for a positive feeding of the entire "sandwich" of material being sewn. This previous "top feeder" is the subject of the U.S. Porter Pat. No. 3,530,809, issued Sept. 29, 1970 and incorporated herein by reference.
While the feeding arrangement described and claimed in U.S. Pat. No. 3,530,809 has enjoyed substantial success, I have realized that various improvements over the feeding arrangement shown in that patent can yield substantially improved performance in various ways: e.g., less wear, smoother and quieter operation, simplicity of repair and interchange of parts, more positive gripping of the material being sewn, etc.
Accordingly, the primary object of the present invention is to provide a top feed arrangement for a sewing machine which has improved performance in one or more of the areas just mentioned.